On September 14th 2015, when researchers discovered the first direct indication of gravitational waves thanks to the echoes of two massive black holes colliding some 1.3 billion years ago, it was a Very Big Deal, as we all know. They'd been searching for them since Albert Einstein predicted them as significant part of general relativity in 1916, but here at last was proof.
What's been not reported, though, is that merely half a second after Laser Interferometer Gravitational-Wave Observatory (LIGO) researchers in Washington and Louisiana spotted the gravitational wave signals, NASA's circling Fermi Gamma-ray Space Telescope discovered a short, faint signal from the same zone in space: Gamma rays likely originating from the same black-hole collision. If this signal turn out to be true, it's an earth-shaking surprise.
Scientists consider that when two black holes combine, they do so "neatly," without generating any light. If these are truly gamma rays, that has to be incorrect. Generating light involves a gas of some sort, and anything like that should have been completely vanished before the black holes even came across each other, or at least main theory goes. Or went.
There appear to be only two potential clarifications. Either the gamma signal was just merely a luck, and that’s not likely, as NASA says there's just a .2% chance of that. Or black holes do discharge gamma rays, which means that scientists have some solid re-thinking to do about black holes’ behavior.
Astronomers' support prize for having a part of black-hole theory possibly blown right out of the sky is that it’s easier to figure out where the big collision took place with three data points than it was with two. Adding the location of the gamma signal has reduced the arc in which scientists think it occurred, from 600 square degrees to 200.